Self Powered Ostogenesis and Osseointegration Promotion and Maintenance Device for Endosseous Implant

ABSTRACT

Osteogenesis and osseointegration promotion and maintenance devices for osseous implants include an implant member having a first electrode, an inlaid second electrode positioned on the member so that it is electrically isolated from and substantially flush with the member surface, and an electrical stimulation mechanism preferably located at the member and operative to provide electrical stimulation signals to endosseous tissue surrounding the implant through the first and second electrodes. The first electrode may be the member itself or a second inlaid electrode. The implant is thus electrically functionalized for osteogenesis and osseointgration acceleration. The device is applicable to both non-dental and dental implants. In all embodiments, the use of inlaid electrode(s) enables the general appearance, external surface and mechanical integrity of the implant to be left essentially unchanged.

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to processes of accelerating bone growth(osteogenesis) and bone tissue healing around endosseous implants. Inparticular, the present invention relates to self-powered devicesincorporated in, or attached to a surgically inserted implant, forexample a dental implant or a hip or knee implant, or devices having anexternal power source, the devices used for accelerating bone growth andhealing in and around the implant surgical site. By “self-powered” wemean devices that include a built-in power source such as a battery. Thefollowing description deals in detail with both dental and orthopedic(non-dental) implants, e.g. hip implants, knee implants, etc.

A major concern for all implants, and in particular non-dental implantssuch as hip or knee implants, is that external appearance, feel, andmechanical integrity and function remain essentially unchanged.Moreover, a surgeon implanting for example a hip implant will prefer tostick to existing procedures even if the implant itself were altered.Presently used implants have undergone decades of development to bebrought to an optimal design. The stringent requirements of implants interms of long term function mean that this optimal design must bepreserved as much as possible in any effort to “functionalize” theimplant for osteogenesis and osseointegration promotion.

It is known that dental implants are widely used, and manufactured by anumber of companies (e.g. Nobel Biocare USA, Inc., 22715 Savi RanchParkway, Yorba Linda, Calif. 92887). Dental implants replace the naturaltooth roots as anchors for the restorative device. As such, they must bewell integrated into the hard bone tissue. The conventional procedurefor inserting a dental implant includes drilling a hole in the maxillaryor mandibular jawbone, and inserting the implant in the prepared hole.Various types of endosseous dental implants are used, e.g. blades,screws, and cylinders. The implant is generally made of titanium ortitanium alloy and the top of the implant is provided with mating means(usually a top portion and inner threads) for attaching the restorativedevice. Before attaching the restorative device, however, there istypically a healing phase of between three to six months, during whichtime bone tissue grows around the implant so that it becomes wellintegrated with the adjacent bone. This is when direct bone-to-implantinterface has been achieved. However, the implant is still at a risk offailure and crestal bone loss within the first year, some of the mainreasons being poor bone strength at the interface, and lowbone-to-implant contact ratio. The primary goal of osteogenesis andosseointegration as related to implants is to increase bone density andimplant-bone contact ratio around any new implant as a routine commonclinical practice.

During the initial and primary healing phase, a cover screw is usuallyattached to the top of the implant to maintain the integrity of the topportion and inner threads of the implant. After the healing phase iscompleted and bone integration has successfully occurred, the coverscrew is removed and discarded and the restorative phase of thetreatment can be initiated. In the initial bone-healing phase, wovenbone is formed around the implant. This type of bone is only partlymineralized, and therefore less able to withstand the high magnitudeforces applied on the implant. The 3-6 month delay between the time ofinsertion of the implant and the time when a restoration can be made isneeded in order for the woven bone to mature and mineralize. The delayis needed because it usually takes this length of time for thebone-forming cells and bone tissue surrounding the implant to maturesufficiently to adequately hold the implant, so that the finalrestoration will be firmly and properly anchored. This delay is a cleardisadvantage of the conventional procedure in use today, leaving thepatients with impaired oral function and esthetics because of themissing teeth. The goal of the restorative dentist is to restore normalfunction and esthetics with no delay, therefore a dual-function deviceis needed: 1) for osteogenesis and osseointegration promotion to fastenand ensure implantation success and 2) a prosthetic design that allowsfor immediate tooth restoration. Such a dual-function device is notknown in the art.

It is also known that orthopedic prosthetic un-cemented components arewidely used alternatives to conventional cemented prostheses. Forexample, a hip joint replacement offers successful rehabilitation ofdamaged joints. The prosthesis can be cemented or un-cemented. Thecemented prosthesis is held in place in the femoral bone by acrylicpolymer cement. Crack fatigue in the cement layer and osteolysis canlead to prosthesis loosening and eventual failure. In the 1980's, a newimplant design was introduced, to attach directly to bone. It was hopedthat cementless prostheses would solve the problems of the cementedprostheses. For un-cemented prostheses, a very exact preparation isneeded because bone cannot bridge a gap of more than 2 mm.

Longer time periods are needed for the rehabilitation process becausebone must be allowed to grow towards and into the prosthesis. Theun-cemented prostheses are implanted in all the patient population, butare recommended mainly for younger and more active patients. Theun-cemented prosthesis may become loosened if a strong bond between stemand bone is not achieved. A long-term successful bond makes theun-cemented prosthesis superior to the cemented acrylicpolymer-dependent prosthesis.

The un-cemented orthopedic implant also needs bone in-growth into theporous surface of the weight-bearing part of the prosthesis (W. H.Harris, “Bony ingrowth fixation of the acetabular component in caninehip joint arthroplasty”, Clin. Orthop, 176; 7, 1983). Animal studieshave shown that only 10% of the prosthesis surface is occupied by boneafter three months. Bone ingrowth into human prostheses may be evensmaller, one of the reasons being the large loads applied by thepatients. Cook et al, in “Histologic analysis of retrieved human porouscoated total joint components”, Clin. Orthop. 234; 90 1988, have foundalmost no bone ingrowth into the porous surface of prostheses retrievedfrom human patients.

It has long been known that the application of electric currents(electric stimulation) can speed bone growth and healing. The electricalstimulation may employ faradic, inductive or capacitive signals. In themid-1960's, C. A. L. Bassett and others measured the weak electricalsignals generated by the bone itself, analyzed and reproduced thosesignals artificially, and used them to reverse osteoporosis or aid inthe healing of fractured bones. E. Fukuda in “On the piezoelectriceffect of bone”, J Physiol. Soc. Jpn. 12:1158-62, 1957, and Yasuda, J.Kyoto Med. Assoc. 4: 395-406, 1953 showed that stress induced oncrystalline components of bone produced current flow. Yasuda showed thatsimilar electric signals could enhance fracture healing. Direct currentcapacitively coupled electric fields and alternately pulsed electromagnetic fields affect bone cell activity in living bone tissue.Friedenberg et al. in “Healing of nonunion by means of direct current”,J. Trauma, 11:883-5, 1971, were the first to report healing of nonunionwith exogenous current. Brighton et al, in “Treatment of recalcitrantnonunion with a capacitatively coupled electric field”, J. Bone JointSurg. Am. 65:577-85, 1985, reported 84% healing of nonunion with D.C.treatment. Time-varying current delivering electrodes have also beenused in order to minimize accumulation of electrode products, whilesquare wave patterns were shown to hasten mineralization during bonelengthening in the rabbit tibia. In his study, Brighton usedcapacitatively coupled electric fields to the limb by capacitor platesover the skin, and accelerated bone fracture healing.

K. S. McLeod and C. T. Rubin in “The effect of low frequency electricalfields on osteogenesis”, J. Bone Joint Surg. 74a:920-929, 1992, usedsinusoidal varying fields to stimulate bone remodeling. They found thatextremely low frequency sinusoidal electric fields (smaller than 150 Hz)were effective in preventing bone loss and inducing bone formation. Theyalso found strong frequency selectivity in the range of 15-30 Hz. At 15Hz, induced electric fields of no more then 1 mV/m affected remodelingactivity. Fitzsimmons et al. in “Frequency dependence of increased cellproliferation”, J Cell Physiol. 139(3):586-91, 1985, also found afrequency specific increase in osteogenic cell proliferation at 14-16Hz. Wiesmann et al. in “Electric stimulation influences mineralformation of osteoblast like cells in vitro”, Biochim. Biophys. Acta1538(1):28-37, 2001 applied an asymmetric saw tooth wave form at 16 Hzand found enhanced bio-mineralization. W. H. Chang in “Enhancement offracture healing by specific pulsed capacitatively coupled electricfield stimulation”, Front. Med. Biol. Eng., 3(1):57-64, 1991, showedsimilar beneficial results at 15 Hz to those achieved by Brighton with a60 KHz sine-wave. Other recent references on faradic stimulation includethe paper by C. E. Campbell, D. V. Higginbotham and T. K Baranowskipublished in Med. Eng. Phys., vol. 17, No. 5, pp. 337-346, 1995(hereinafter CAM 95), and U.S. Pat. No. 5,458,627 to Baranowski andBlack. Studies related specifically to dental bone tissue are alsoknown, and a number of patents disclose related systems, for exampleU.S. Pat. No. 4,244,373 to Nachman. However, the art that relatesspecifically to dental bone growth stimulation by small, self poweredelectrical means is very limited.

U.S. Pat. No. 5,292,252 to Nickerson et al. discloses a stimulatorhealing cap powered by an internal small battery. The cap can bereversibly attached to a dental implant, and stimulates bone growth andtissue healing by application of a direct current path orelectromagnetic field in the vicinity of bone tissue surrounding theimplant, after the implant is surgically inserted. While Nickerson doesnot provide details of the battery, it is clear from his descriptionthat his battery is volumetrically extremely small, thus having verysmall capacity, which may not suffice for effective DC stimulation.Moreover, DC stimulation is known to have negative side effects. Forexample, Kronberg in U.S. Pat. No. 6,321,119 points out that studies onelectrical stimulation of bone growth have shown that application of DCstimuli alone may be problematic in stimulating bone regeneration sincebone grows near the cathode (i.e. the negative electrode), but oftendies away near the anode. This phenomenon may result from electrolyticeffects, which can cause tissue damage or cell death through pH changesor the dissolution of toxic metals into body fluids. Other disadvantagesof Nickerson's device include: being sunken into the gingiva, it has aninternal volume too small to contain a large enough battery. Its shapecauses great discomfort upon removal. The healing cap is connected tothe implant by a thin, weak plastic rod that may break during normalchewing Its insulation section is larger than the battery itself,limiting the size of the battery even more.

AC (alternating current) signals may work better in electrotherapy thanDC (direct current) signals, and pulse bursts may be more effective thansingle pulses. For this reason, many bioelectronic bone growthstimulators rely solely on AC effects, removing any net DC current fromthe outputs by passing the signal through a blocking capacitor. Such acapacitor forces the positive and negative output currents, when summedover a full cycle of the output waveform, to be equal, canceling eachother out.

Although bone growth stimulation by AC or pulsed currents is deemedbeneficial, there are no known practical, self-powered, compact dentalstimulator caps using such currents. A somewhat related device disclosedby Sawyer et al. in U.S. Pat. No. 4,027,392 lacks enough description towarrant detailed discussion. Sawyer's disclosure mentions an embodimentof a bionic tooth powered by a battery and including an AC circuit thatis clearly impractical: among major disadvantages, it does not appear tobe removable without major surgery (since removal of his upper portion26 occurs by unscrewing insulating member 30 from external implantthread 22, thus causing major trauma to the extensive gingival areacontacted by portion 26); it uses a preferred signal frequency range of0.5 to 1 mHz; and it cannot provide current pulses. The micro-circuitryindicated by its FIG. 3 is not shown incorporated within the cap, and itis extremely doubtful that it can be implemented in the system shown.Its battery cap (“crown”) is too long, penetrating deep into the gingiva(or even through the bone), thus being unfeasible and useless from asurgeon's point of view. Also, Sawyer's device is not a dual-functiondevice, i.e. it does not serve as a temporary abutment on which one caninstall a temporary crown.

Another related device is disclosed by Dugot in U.S. Pat. No. 5,738,521.Dugot describes a method for accelerating osseointegration of metal boneimplants using AC electrical stimulation, with a preferably symmetrical20 μA rms, 60 KHz alternating current signal powered by a small 1.5 Vbattery. However, Dugot's system is not a compact, self-poweredstimulator cap, but a cumbersome, externally (to the implant) wired andpowered stimulator, which does not appear to be feasibly applicable tohuman dental implants.

Osteogenesis devices for non-dental implants include interbody fusiondevices as described in U.S. Pat. No. 6,605,089B1 to Michelson.Michelson describes a self contained implant having a surgicallyimplantable, renewable power supply and related control circuitry fordelivering electrical current directly to an implant which is surgicallyimplanted within the intervertebral space between two adjacentvertebrae. Electrical current is delivered directly to the implant andthus directly to the area in which the promotion of bone growth isdesired. However, Michelson's apparatus is not an adaptation of areadily available implant, nor does it have an optimal configuration ofelectrodes.

Other devices are disclosed in U.S. Pat. No. 4,026,304 to Levy, U.S.Pat. No. 4,105,017 to Ryaby, U.S. Pat. No. 4,430,999, 4,467,808 and4,549,547 to Brighton, U.S. Pat. No. 4,509,520 to Dugot, U.S. Pat. No.4,549,547 to Kelly and U.S. Pat. No. 5,030,236 to Dean, and in a recentUS patent application No 20030040806 by MacDonald.

U.S. Pat. No. 6,034,295 discloses an implantable device with abiocompatible body having at least one interior cavity that communicatesthrough at least one opening with the surroundings of the body so thattissue surrounding the implantable device can grow through the opening;two or more electrodes within the device having terminals for supplyinga low-frequency electrical alternating voltage and at least one of whichis located inside the cavity. U.S. Pat. No. 5,030,236 also discloses theuse of electrical energy that relies upon radio frequency energy coupledinductively into an implanted coil to provide therapeutic energy. U.S.Pat. Nos. 5,383,935, 6,121,172, 6,143,035, 6,120,502, 6,034,295, and.5,030,236 all relate to the use of various materials and forms of energyto enhance the regrowth of bone at the interface between an implantedprosthesis and the native bone. None of these devices performsatisfactory osteogenesis promotion, maintenance or acceleration whileleaving the implant member or stem essentially unchanged in appearanceand mechanical properties.

There is thus a widely recognized need for, and it would be highlyadvantageous to have, practical, self-powered osteogenesis andosseointegration promotion and maintenance devices for endosseousimplants that can perform electrical stimulation using various signals.It would also be extremely advantageous that such devices, when used forexample in hip or knee implants, should require minimal changes to bothappearance and mechanical integrity and function of the implants. Theprimary goal of such devices would be to increase bone density andimplant bone contact ratio around any new implant as a routine commonclinical practice. In the case of dental implants, such a device shouldpreferably serve also as an abutment for a prosthetic crown thatimmediately restores oral function.

SUMMARY OF THE INVENTION

According to the present invention there is provided an osteogenesis andosseointegration promotion and maintenance device for an osseous implantincluding an implant member having a conductive surface and operative toserve as a first electrode, an inlaid second electrode positioned on themember so that it is electrically isolated from and substantially flushwith the surface, and a stimulation mechanism operative to provideelectrical signals to an endosseous tissue surrounding the memberthrough the first and second electrodes.

According to the present invention there is provided an osteogenesis andosseointegration promotion and maintenance device for an osseous implantincluding an implant member having a surface, a first electrode inlaidin the surface, a second electrode inlaid in the surface andelectrically isolated from the first electrode, and a stimulationmechanism located at the member and operative to provide electricalsignals to an endosseous tissue surrounding the member through the firstand second electrodes.

According to the present invention, there is provided a self poweredosteogenesis promotion device including a tissue-contacting body havingan external surface in contact with biological tissue and having ahollow enclosure, a conductive element in electrical communication withthe hollow enclosure and electrically isolated from the externalsurface, and an electrical stimulation mechanism located within thehollow enclosure for providing electrical stimulation to the biologicaltissue through the conductive element, wherein the electricalstimulation is enhanced stimulation.

According to the present invention, there is provided a self poweredosteogenesis and osseointegration device including an implant member, anelectrode positioned on the member so that the electrode is electricallyisolation from a surface of the implant member, and a stimulationmechanism operative to provide electrical stimulation signals to anendosseous tissue surrounding the member through the electrode, whereina position of the electrical stimulation mechanism of the electroderesults in an essentially unchanged external appearance and mechanicalintegrity of the implant member.

According to the present invention there is provided a method forosteogenesis and osseointegration promotion and maintenance involving animplant member implanted in the human body, comprising electricallyfunctionalizing the implant member while keeping its external appearanceand mechanical integrity essentially unchanged, and using theelectrically functionalized implant member to promote osteogenesis andosseointegration of osseous tissue with the implant member.

According to the present invention there is provided a self poweredosteogenesis and osseointegration promotion and maintenance device foruse with a dental endosseous implant, including a hollow enclosurehaving an electrically biocompatible conductive external wall insubstantial electrical contact with the gingiva and insulated from theimplant, a biocompatible metallic screw for reversibly attaching theenclosure to the implant, the screw electrically insulated from theexternal wall, and an electrical stimulation mechanism for providingelectrical stimulation signals to the endosseous tissue.

According to the present invention there is provided a dual-functiontemporary abutment capable of osteogenesis and osseointegrationpromotion and maintenance and simultaneously capable of restoring postimplantation oral function due to prosthetic crown-supporting design,the abutment attachable to a dental implant, including an internallyhollow enclosure configured to be attached to a temporary dental crown,a metallic screw for facilitating the attachment of the abutment to theimplant, the screw mechanically coupled to, and electrically insulatedfrom the enclosure, and an electrical stimulation mechanism locatedpreferably inside the hollow enclosure, the mechanism operative toprovide stimulation signals in an external electrical path including theabutment and the implant.

According to the present invention there is provided a method forosteogenesis and osseointegration promotion and maintenance in a dentalimplant while restoring post-implantation oral function, includingproviding an electrical stimulation mechanism enclosed within adual-function temporary abutment attachable to the dental implant,attaching a temporary dental crown to the abutment; and activating thestimulation mechanism, thereby providing a plurality of current pathsbetween the abutment and the implant, whereby currents flowing in thecurrent paths promote and maintain osteogenesis and osseointegration.

According to the present invention there is provided a self poweredosteogenesis and osseointegration promotion and maintenance deviceintegrated with a hip implant, including a partially hollow implantmember having an electrically biocompatible conductive externalenvelope, at least one stimulation electrode encircling the member andinsulated electrically from it, and an electrical stimulation mechanismfor providing electrical stimulation signals to the endosseous tissue,the stimulation mechanism connected with one polarity to the member andwith another polarity to the at least one stimulation electrode.

According to the present invention there is provided a dual-functiontemporary abutment capable of osteogenesis and osseointegrationpromotion and maintenance and simultaneously capable of restoring postimplantation oral function, the abutment attachable to a dental implant,the abutment including an internally hollow enclosure, a temporary crownattached to the enclosure, means to attach the enclosure to the dentalimplant, and an electrical stimulation mechanism enclosed within theenclosure and operative to provide stimulation signals in an externalelectrical path including the abutment and the implant, whereby thestimulation promotes osteogenesis and osseointegration between theimplant and an endosseous tissue, and whereby the temporary crownrestores oral function immediately after the implantation.

According to the present invention, there is provided a device forosseointegration, including a titanium implantable member having asurface with a groove, and an inlaid electrode placed in the groove, alayer of titanium oxide applied to the surface, insulating the inlaidelectrode from the surface, and a stimulation mechanism operative toprovide electrical stimulation signals to an endosseous tissuesurrounding the member through the inlaid electrode.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Although methods and materialssimilar or equivalent to those described herein can be used in thepractice or testing of the present invention, suitable methods andmaterials are described below. In case of conflict, the patentspecification, including definitions, will control. In addition, thematerials, methods, and examples are illustrative only and not intendedto be limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, withreference to the accompanying drawings, wherein:

FIG. 1 shows a preferred embodiment of the osteogenesis device of thepresent invention as implemented in dental implants in (a) isomeric viewand (b) cross-section;

FIG. 2 shows another preferred embodiment of the dental osteogenesisdevice of the present invention in (a) isomeric view and (b)cross-section;

FIG. 3 shows yet another preferred embodiment of the dental osteogenesisdevice of the present invention in cross-section;

FIG. 4 shows the device of FIG. 1 inserted with its bottom screw sectioninto a dental implant: (a) isomeric view; (b) cross-section; and (c) anactive abutment connected to an implant with a single inlaid electrode.

FIG. 5 shows a schematic diagram of a stimulation mechanism comprising amicro-battery connected to an electronic device;

FIG. 6 shows a micro-battery from the device of FIG. 5, wherein themicro-battery is a three-dimensional thin film micro-electrochemicalcell;

FIG. 7 shows an embodiment of a stimulation mechanism that includes amicro-electrochemical cell integrated with electronic devices;

FIG. 8 shows an embodiment of a stimulation mechanism that includescontrol means;

FIG. 9 shows an embodiment of a stimulation mechanism that furtherincludes activation means;

FIG. 10 (a-c) shows schematically a preferred embodiment of theosteogenesis device of the present invention as applied to hip implants,having a spiral winding inlaid electrode;

FIG. 11 shows schematically another embodiment of the osteogenesisdevice of the present invention as applied to hip implants, havinglongitudinal parallel inlaid electrodes;

FIG. 12 (a-c) shows various embodiments of the osteogenesis device ofthe present invention as applied to hip implants, having ring inlaidelectrodes: a) rings connected to common internally threaded lead; b)rings connected to common an external inlaid lead; and c) separate ringsets connected respectively to a first and a second external inlaidlead;

FIG. 13 shows yet another embodiment of the osteogenesis device of thepresent invention as applied to hip implants having separate dot inlaidelectrodes;

FIG. 14 shows an embodiment of the osteogenesis device for a hip implantwith two crisscrossed helix inlaid electrode on a non-conductivesurface; and

FIG. 15 shows the device of FIG. 10 in an embodiment in which thefunctionalized implant uses direct currents to induce osteogenesis.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention discloses, in various embodiments, an osteogenesisand osseointegration promotion and maintenance device (hereinafter“osteogenesis device”) for endosseous implants, capable of providing DC,AC and arbitrary current train pulses, or any combination thereof. In apreferred embodiment in which the osteogenesis device is self-powered,the device preferably uses as power source an internal battery that maybe miniaturized (i.e. a microbattery). The microbattery may be furtherintegrated with electronic and/or actuating circuitry. Alternatively,the osteogenesis device can be powered remotely from outside the body.In embodiments of devices with extremely small internal cavity volumes(such as a dental implant) that cannot use conventional batteries, theinternal battery is preferably a three-dimensional (3D) thin filmmicro-electro-chemical cell as described in U.S. Pat. No. 6,197,450 toNathan et. al. The micro-electro-chemical cell may be integrated on thesame silicon chip with the microcircuit that controls output signals.Any internal power source relevant to the present invention willhereafter be referred to as a “microbattery”, while the microcircuitthat controls output signals will be referred to as a “stimulationcircuit or device”. A power source plus stimulation device will bereferred to as “stimulation mechanism”. For the sake of simplicity, theterm “microbattery” will be applied hereinbelow also to regularbatteries that may be used internally in implants that are not small,e.g. hip or knee implants. Separate descriptions are given below fordental implants and non-dental (e.g. hip) endosseous implants that usethe osteogenesis device. In some embodiments, the osteogenesis deviceand the implant are integrated in one piece, i.e. the osteogenesisdevice is an integral part of the implant. That is, the implant ismodified to become a “functionalized” (for osteogenesis acceleration)implant. The principles and operation of an osteogenesis device forendosseous implants according to the present invention may be betterunderstood with reference to the drawings and the accompanyingdescription.

Osteogenesis Devices In Dental Implants

Referring now to the drawings, FIG. 1 shows a preferred embodiment ofthe osteogenesis device of the present invention, as applied to dentalimplants. FIG. 1 shows an isometric view of a temporary osteogenesisabutment 20 in (a) and a cross-section in (b). Temporary abutment 20includes a top section 22, a mid-section 24 and a bottom screw section26. In a preferred embodiment, sections 22 and 24 are made of one piece,and referred to as an “enclosure” 25 section of the abutment. Topsection 22 is preferably cylindrical and internally hollow, with aheight h₁ between ca. 3-12 mm, preferably between 3-8 mm, and mostpreferably around 5 mm; a diameter Φ₁ of between 2.5 and 6 mm,preferably between 3.5 and 4.5 mm, and most preferably around 3.75 mm.Top section 22 has a cylindrical envelope wall 27, the same wallextending to mid-section 24 in case the two sections are integrated. Forthe purposes of the present invention, the optimal thickness of wall 27is the smallest thickness still ensuring mechanical stiffness andintegrity of the abutment, while bonded to a temporary crown, see FIG. 2and description below. Typically, this thickness is about 0.5-1 mm.Height h₁ depends on the height of the individual tooth to be attachedto abutment 20, see below. Top section 22 is preferably made of a metalused normally in present dental abutments, for example titanium, and hasan external cylindrical surface 28 prepared or treated to bond to atemporary crown 30 as shown in FIG. 4 a. However, section 22 may be madeof other materials, such as ceramics or hard plastics, as long as itfulfills the mechanical requirements. Mid-section 24 is structured toensure at its top plane 32 a perfect match to temporary crown 30, whileits side envelope 34 is shaped to allow easy removal upon completion offunction. As shown, envelope 34 is preferably conical. Section 24 may besubstantially hollow internally and, as pointed out above, mayintegrally form an “enclosure” of one piece with top section 22, as seenin FIG. 1( a), as well as in FIGS. 2 and 3. Mid-section 24 is made of anelectrically conductive rigid material, preferably a metal such astitanium. If integrated with top section 22, the top section is madepreferably of the same material, and its wall must be electricallyconductive in a contact area with the gingiva, see FIG. 4. Typicaldimensions of envelope 34 are a small diameter Φ₂ (that presents anemerging profile of the abutment from the gums) of between 3.25 to 6 mm,and most typically around 3.75 mm, a large diameter Φ₃ matching thediameter of typical dental implants, currently between 5 and 6 mm, and aheight h₂ of typically between 1-4 mm. Mid-section 24 is partially orfully immersed in the gum (gingiva), see FIG. 4, while top section 22 isessentially located on top of the gingiva.

Bottom screw section 26 is metallic, normally made of titanium, andessentially identical with screws typically used to attach existingabutments to dental implants, such as an implant 50 shown in FIG. 4.Screw section 26 is electrically isolated from enclosure 25 by anelectrical insulating separator 110, preferably in the shape of a disc.

FIG. 2 shows in isomeric view in (a) and in cross-section in (b) anotherembodiment of a temporary abutment 20′ according to the presentinvention. Abutment 20′ is essentially identical in all with abutment 20of FIG. 1, except for a conical top section 22′ replacing cylindricaltop section 20. Conical top section 22′ provides more internal volume tocontain the stimulation mechanism, control means and activation meansdescribed below. Section 22′ is typically of a small diameter and aheight similar to those of section 22 above, while having a largediameter Φ₄ close to, and no larger than Φ₃.

FIG. 3 shows (in cross section only) an embodiment of a temporaryabutment 20″ according to the present invention wherein a top section22″ is of a combined cylindrical-conical shape, to be referred tohereafter as “angular”. An angular shape is of particular importance forabutments in anterior teeth, and for abutments in anterior and posteriorjaw areas because of the angulation of the teeth in the bone. Theangulated abutments allow for treatment of angulated implants—a clinicalsituation often encountered in the maxilla (upper jaw). As made clear bythe figure, top section 22″ has a cylindrical envelope section 40smoothly translating into a conical envelope section 42. A top smalldiameter Φ₅ is now typically smaller than Φ₁ while all other dimensionsare essentially similar to those in FIGS. 1 and 2. The dental implantembodiment of the invention is now further described based on theembodiment of FIG. 1, with the understanding that the followingdescription applies equally well to the embodiments of FIGS. 2 and 3.

FIG. 4 shows the abutment 20 of FIG. 1 inserted with its bottom screw 26into dental implant 50, and its top section 22 attached to a temporarycrown 30. The figure shows an isomeric view in (a) and a cross-section(without a crown) in (b). FIG. 4( a) also shows an adjacent tooth 60with a crown 62 and a root 64. In contrast with previous devices, inparticular those of U.S. Pat. Nos. 4,027,392 and 5,292,252, the deviceof the present invention is not only a stimulation device but also atemporary crown-carrying abutment. Moreover, abutment 20 is designed toresemble as much as possible existing abutments, thus not requiring anychanges in normal dental surgery procedures, while temporary crown 30can be individually shaped for each patient. The latter is a criticalrequirement for such a dual-function device, and a feature that isnon-existent in any of the prior art patents. Since the dual-functiondevice (temporary abutment) of the present invention typically resemblesexisting abutments, its removal and replacement with a permanent crownrequires advantageously a standard surgical procedure, unlike specialsurgical procedures needed in prior art devices.

FIG. 4( b) shows in cross section abutment 20 attached to dental implant50 implanted in an osseous tissue 52 below gingiva 54. The figure showsthe typical positioning of mid-section 24 relative to the top of agingiva 54. Abutment 20 may in some cases stick out upwards from gingiva54. However, in all cases, mid-section 24 maintains electrical contactwith the gingival tissue.

Implant 50 is preferably a standard metal (preferably titanium)electrically conductive implant manufactured by a number ofmanufacturers and well known in the art. The figure shows the internalstructure inside top section 22 and mid section 24, which ismechanically coupled to implant 50 through screw section 26, whileelectrically insulated from implant 50 by electrically insulatingseparator 110. In a preferred embodiment, electrically insulatingseparator 110 is titanium oxide. Top section 22 may optionally have aremovable top plate 70 attached (e.g. screwed in) to cylindrical wall27, and a socket 72 that may aid in opening the top plate, or removingthe entire abutment from implant 50. Separator 110 is preferably of aminimal shape and size that ensure electrical isolation between screw 26and implant 50 and sections 22 and 24, while imparting mechanicalstrength to the abutment-implant connection. Separator 110 may be madeof any insulating biocompatible material, for example plastic such asTeflon, ceramic, glass, hard rubber, etc. The essential requirement isthat mid-section 24 be at least partially in electrical contact withgingiva 54, while electrically isolated from implant 50. Separator 110is bonded to mid-section 24 and screw 26 in a way that provides bothcomplete sealing between the internal space inside the abutment and theoutside, as well as a strong enough mechanical hold for screw 26. Suchbonding and sealing may be provided by means including a ceramic seal, ametal-glass seal or a glass-epoxy seal, which are well known in the art.

As mentioned, top section 22 as well as (at least partially) mid-section24 (i.e. enclosure 25) are internally hollow, allowing inclusion of anelectrical stimulation mechanism 113 comprised of an internalmicro-battery 114 and at least one electronic device 116. Using typicaldimensions of Φ₁=3.75 mm and wall thickness of 0.5 mm (i.e. the internaldiameter of top section 22 is ca. 2.75 mm) and h₁=8 mm, the internalvolume of section 22 is about 40-45 mm³. With h₁=5 mm, the volume wouldbe around 25-28 mm³. Section 22′ in FIG. 2 has a larger internal volume.Micro-battery 114 may be a small standard type battery, preferably aLithium battery, or a thin film battery, preferably themicro-electro-chemical cell described in U.S. Pat. No. 6,197,450. Asdescribed in more detail in FIG. 5 below, in one embodiment,micro-battery 114 is electrically connected with both polarities todevice 116 through electrical contacts 80 and 82. Device 116 isconnected with one polarity through a contact 118 to the electricallyconductive envelope of enclosure 25, and with another polarity, throughscrew 26 to implant 50. In another embodiment (not shown), micro-battery114 may be connected with one polarity to device 116, and with anotherpolarity to either enclosure 25 or screw 26, in which case, device 116is connected with the other polarity to screw 26 or enclosure 25respectively. In either embodiment, an electrical path 120 is thusestablished between mid-section 24 and implant 50 through the tissuecomposed of gingiva 54 and osseous tissue 52. Electrical path 120 isactive (passing current) when micro-battery 114 is connected in thecircuit comprising abutment 20, implant 50, osseous tissue 52 andgingiva 54. Path 120 is inactive (no current) when source 114 isdisconnected from the circuit, preferably as a result of inputs receivedthrough device 116. One task of device 116 is to convert the DC power ofmicro-battery 114 into AC or pulsed voltages or currents. Another taskof device 116 is to provide timing for current pulses. Yet another,optional task of electronic device 116 is to relay and performinstructions from a source external to abutment 20, to activate andde-activate path 120. Device 116 includes most preferably at least oneintegrated circuit acting as a stimulation circuit, and additionally andoptionally as a timing/control circuit, operative to fulfill the taskslisted above, as described in more detail below.

As mentioned above, the electrical stimulation provided by device 20through at least one electronic device 116 is preferably in the form ofAC currents or pulsed DC currents. It should be apparent that anyconfiguration of AC or DC currents may be used alone or in combination,and switching may occur between the types of current used. Theconversion of direct current signals, normally provided by a constantpower source in the form of a battery or a micro-electro-chemical cell,to AC or pulsed DC signals is well known in the art. In particular,various electrical circuits that perform DC to AC conversion, orgenerate pulses from a DC voltage or DC current source are known. Suchcircuits include various signal generators and waveform shaping circuitsdescribed for example in chapter 12 of “Microelectronics Circuits” by A.D. Sedra and K. S. Smith, ISBN 0-03-051648-X, 1991, pp. 841-902.Implementation of such circuits (and particularly of oscillatorcircuits) in integrated (IC) form is also known, for example in U.S.Pat. No. 6,249,191 to Forbes. Low voltage IC circuit architecturessuitable for the purposes of the present invention include for examplethe LM3903 1.3V oscillator by National Semiconductor, described inApplication Note 154 (AN-154) of the same company. Notice is taken thatsuccessful implementation of a combination of a micro-battery and aDC-to-AC converter or pulse generator circuit in a limited space such asthe volume inside enclosure 25 has not been accomplished in prior art,and there are no known products or even prototypes of such combinations.For example, the osteogenesis promoting pulse generator disclosed inU.S. Pat. No. 5,217,009 to Kroneberg is not integrated on a chip, butmounted on a circuit board of relatively large (2.5×5.0 cm) dimensions,the final size requiring a volume of 1.7×2.5×9.5 cm³. Thus prior artpulse generators are of no use for the purposes of the presentinvention.

The technical requirements of a stimulation device such as electronicdevice 116 as relating to dental implants are preferably the following:the device should supply a voltage in the range of 1 micro-Volt to 10Volt, and most preferably between 100 μV to 1V, with a frequency in therange of 1 Hz to 100 KHz, preferably in the range of 5 Hz to 50 Hz, andmost preferably between 10 to 20 Hz; these voltages will supply an ACoutput current with an amplitude between 1-300 μA/cm². For a pulsedsignal, the signal should be at a voltage in the general range above.Pulse burst patterns that may be effective for the purposes of thepresent invention are characterized for example by waveforms describedin FIGS. 1, 2, 7 and 9 of U.S. Pat. No. 6,321,119 to Kronberg. Forexample, in FIG. 1 therein, pulse bursts are characterized by intervals14 (representing peak voltage or current amplitude), and intervals 16(“off”), and 18 (“on”), representing the timing between specifictransitions. In the present invention, pulse bursts preferably rangefrom continuous to patterns with “on” intervals of between 1-10 msec andpreferably 5 msec, and “off” intervals of between 100 to 4000 msec, andpreferably between 500 to 2000 msec. These patterns can be defined thenin terms of an average frequency of between ca. 15-600 Hz, andpreferably between 30-120 Hz. The low preferred frequencies disclosedherein for both AC and pulsed signals are in marked contrast with theorders of magnitude higher frequencies used in prior art stimulationsystems.

FIG. 4( c) shows an embodiment of an “active abutment” using a spiralwinding inlaid electrode 160, connected to stimulation mechanism 113through a lead 118 and a feedthrough 162. Inlaid electrodes arediscussed in detail with reference to non-dental implants below. Inlaidelectrodes in activated implants may have any of the embodiments (interms of inlaid electrode configurations) shown in FIGS. 10-14 below. Inparticular, ring, straight line, dot and double inlaid electrodeconfigurations described therein are also suitable for active dentalabutments.

FIG. 5 shows in more detail a schematic diagram of stimulation mechanism113 of FIG. 4 comprising micro-battery 114 connected to electronicdevice 116. Micro-battery 114 includes two terminals of oppositepolarities 402 and 404. Electronic device 116 includes two electricalinput ports 406 and 408, and two electrical output ports 410 and 412.Input ports 406 and 408 are electrically connected to terminals 402 and404, while output ports 410 and 412 are electrically connectedrespectively to wall 27 of enclosure 25 through contact 118 and to screw26. Thus, in contrast with prior art internal batteries used forstimulation in implants, e.g. those of U.S. Pat. Nos. 4,027,392 and5,292,252, battery 114 may not need to be in direct electrical contactwith any part of enclosure 25 or implant 50. A key requirement of means113 is that it completely reside inside enclosure 25. Therefore,micro-battery 114 has dimensions smaller than the internal dimensions ofenclosure 25. In particular, if micro-battery 114 is a conventionalbattery, preferably a Lithium battery of cylindrical shape, its cylinderdiameter has to be no larger than the internal diameter of theenclosure, while its height has to be sufficiently smaller than theinternal enclosure height to leave space for device 116. In a preferredembodiment, battery 114 and device 116 are positioned as shown in FIG.4, i.e. with the battery on top. However, an inverse positioning(battery 114 below device 116) as well as same plane positioning(side-by-side) of the two elements is also possible, and within thescope of the present invention.

In a yet another preferred embodiment, shown in FIG. 6, battery 114 is a3-D thin film micro-electrochemical cell as disclosed in U.S. Pat. No.6,197,450. In this embodiment, cell 114 is most preferably implementedon a semiconductor substrate such as silicon or Gallium Arsenide in theform of a battery “chip”. In order to fulfill the preferred powerrequirements above, cell 114 is typically built on a silicon or GaAswafer of standard thickness used in microelectronic integrated circuits,i.e. 300-600 μm, with an original (before perforation) area from about 1mm² to about 40 mm². hi this embodiment, cell 114 and device 116 (whichis an integrated circuit) can advantageously be packaged together usinga multi-stack structure mounted on a chip scale package (CSP). CSP's arewell known in the art, come in a wide variety of dimensions, materials,etc., and are described in detail for example in chapter 15 of IntelCorporation's 2000 Packaging Databook. One of the main advantages of aCSP is that its size is only ca. 20% larger than that of the chipsmounted on it. Thus, the internal volume of enclosure 25 described abovecan easily accommodate for example the “1-Wire” CSP manufactured byDallas Semiconductor, which has a footprint of 0.77 mm length×1.3 mmwidth×0.43 mm height. Other CSPs as well as other type of packages, forexample the Mini SOIC package manufactured by Intel Corporation anddescribed in the same Databook may be equally useful for the purposes ofthe present invention.

In yet another preferred embodiment shown in FIG. 7, cell 114 isintegrated on the same semiconductor chip 600 with one or morestimulation integrated circuits 602 of electronic device 116. That is,cell 114 and DC-to-AC circuits or pulse generating circuits generatingthe stimulation signals comprise one integrated, self-poweredstimulation chip.

As mentioned, in certain applications, it is desirable that theamplitude, timing and duration of the stimulation pulses becontrollable, as described for example in U.S. Pat. No. 5,217,009 toKronberg. Such control may be implemented by control means in the formof an integrated circuit 702, which is shown in FIG. 8 incorporated indevice 116. Control circuits include various timing circuits well knownin the art and described for example in Sedra and Smith above.Off-the-shelf timing circuits useful for the purposes of the presentinvention include the “555” family of devices by National SemiconductorCorp., for example the LM555 timer operable at 5V. The control circuitrymay advantageously be integrated with the stimulation circuitry alone,or with both battery 114 and stimulation integrated circuits 602, thusproviding an extremely compact device 116. Such integration is bestimplemented by designs and technologies known under the general mane oflow-power, low-voltage, mixed signal ASICs (application specificintegrated circuits). The battery, preferably a 3-D thin-film cell, andthe stimulation and control circuitry, each implemented on asemiconductor integrated circuit, can advantageously be stacked andmounted together on a small-footprint package such as the CSP mentionedabove.

In an alternative embodiment shown in FIG. 9, activating means 802, forexample an RF, piezoelectric or magnetic element pre-programmed toreceive activation orders from an external (to the mouth) activator, isadded to device 116. Element 802 is used to externally effect theoperation of control means 702, that is to instruct means 702 to startand stop the operation of device 116. In other words, element 802activates or de-activates electrical path 120 upon externalinstructions. The activating and de-activating is best seen as,respectively, the closing and opening of the electrical connectionbetween either one or both of the output ports of device 116 andenclosure 25 or screw 26 or both. Element 802 is of small dimensionscommensurate with the internal space limitations of enclosure 25. In oneembodiment, element 802 may be a thin-film piezoelectric actuatormanufacturable by known thin-film processes. When such processes arecompatible with the integrated process for manufacturing the integratedcell-stimulation circuit combination of FIG. 7, element 802 may beintegrated with battery 114 and stimulation integrated circuits 602 onthe same semiconductor chip. The actuator, as a discrete element or whenimplemented on an IC, is advantageously added to the stack mounted on aCSP as described above, providing a compactly packaged, self-poweredcombination of stimulator-control-activator device.

Osteogenesis Devices in Orthopedic (Non-Dental) Implants

FIG. 10 shows schematically a preferred embodiment of the osteogenesisdevice of the present invention, as applied to orthopedic implants. FIG.10( a) shows an implant 1000 (shown exemplarily as a hip implant) madeof a biocompatible material, preferably titanium. The implant has anelongated member 1002 with a length axis 1004. Member 1002 has anelectrically conductive external surface 1006, and ends in an endsection 1008. End section 1008 can be similar, for example, to topsection 22 of dental abutment 20, described above. Essentially, endsection 1008 is internally hollow, and has at least one isolatedfeedthrough for connecting wires therethrough. Such feedthroughs arecommonly known in the art.

Preferably, the hip implant is of a size and shape provided bymanufacturers of such implants. The present invention advantageouslyprovides an osteogenesis stimulation function to such an implant withminimal external changes to its structure and mechanical properties.Typically, member 1002 is solid (full) and its conductive surface 1006is treated and primed to provide a good surface for osteogenesis andbone tissue healing when implanted into a bone (e.g. the femur bone).Preferably and advantageously, the present invention minimizes anychanges in this external surface and in the general shape of theimplant, while providing the necessary electrical stimulation functionto accelerate osteogenesis. The stimulation requires ideally uniformlydistributed electric fields (and currents) proximate to the implantsurface, the fields and currents supplied by two electrodes, surface1006 serving as one electrode. In an embodiment having DC stimulation,surface 1006 serves as the negative electrode. In the preferredembodiment of FIG. 10, a second, thin electrode 1010, electricallyinsulated from surface 1006 is spun as a spiral winding in anappropriate geometry around member 1002 inside an electrically insulatedgroove 1012 formed in the member, preferably such that the spunelectrode is externally flush with surface 1006. This electrode is thus“inlaid” in the implant, as shown in detail (b). The winding has a pitchP, which can be varied according to predetermined specifications.

Inlaid electrodes are well known in the art of integrated semiconductorcircuits where they are referred to as “damascene” conductors. However,there is no known use of inlaid, “damascene” type electrodes inimplants. “Damascene techniques” are well known for inlays of variousmetals such as gold, copper, etc in a substrate, normally but notnecessarily metallic. The use of the term “inlaid” herein means to coverall geometries of an electrode conductor sunken flush into an implantmember surface, preferably (but not necessarily) such that the originalmember surface topology remains essentially unchanged. Those skilled inthe art of semiconductors will also be familiar with the term “dualdamascene” used for two inlaid and overlapping conductors, isolated fromeach other everywhere except at a contact via. A similar “dualdamascene” geometry or structure is described hereinbelow with respectto FIG. 12( c), in which however, the two conductors are electricallyisolated from each other everywhere, with no conducting via.

Electrode 1010 is preferably a very thin wire or ribbon made of abiocompatible conductive material, e.g. gold or platinum, as shown inmore detail in the insert in FIG. 10( b). The use of a material such asgold or platinum enables the wire to be formed with extremely smalldiameters, thus enabling minimization of changes in the implant surfacestructure. The wire may be inserted mechanically in the insulatedgroove, pasted in as a thick film, or deposited using various thin-filmdeposition techniques known in the art of damascene techniques. Theinsulation between electrode 1010 and surface 1006 may be provided forexample by a thin insulator film 1014 deposited, inlaid, or otherwisegrown (e.g. grown anodically in the case of titanium oxide on titanium)inside the groove. For a conducting member, the insulator is formed onlyin the groove, while the rest of the implant surface remains conducting.It is known that titanium anodic oxides may be grown to thicknesses froma few Angstroms to a few microns using techniques well known in the art,and provide excellent electrical isolation. Alternatively, theinsulation may be provided by an inlaid biocompatible non-conductor,such as a thin plastic, polymer or ceramic sleeve. Advantageously, aninlaid electrode in the embodiments of FIGS. 10 and 11 (see below) needsonly one point of contact to one lead of the internal power source, asdiscussed further below. This simplifies the design, by requiring onlyone electrical feedthrough 1020 in end section 1008, as shown in (c). Itshould be noted that the use of titanium oxide can in itself enhancebone ingrowth, as is known in the art. Thus, the use of titanium oxideas an insulator may serve two purposes: to insulate, and at the sametime to provide additional osseointegration effects.

FIG. 11 shows an embodiment in which an inlaid electrode 1010′ is formedas lines substantially parallel with length axis 1004 and commonlyconnected to one lead of stimulation mechanism 1030 (shown in FIG. 10 c)through a single feedthrough 1020′ in member end section 1008. It willbe apparent to one skilled in the art that the lead can be split eitherinternally or externally to the member body, so that not all lines 1010′are connected to the same single split lead. In particular, when splitinternally, there may be more than one feedthrough through the memberend section, each feedthrough containing one split lead which thenconnects to one or more lines 1010′. If the member surface isnon-conductive, the “line” electrodes may be split into two sets ofalternating lines comprising a “first” and a “second” electrode, eachset (electrode) connected through a separate feedthrough and separatelead to the stimulation mechanism (not shown). In this way, anon-conductive material may be used for the implant, while stillmaintaining a dual electrode system.

FIG. 12 (a-c) shows various embodiments of the osteogenesis device ofthe present invention as applied to hip implants, having ring inlaidelectrodes: a) rings connected to a common internally threaded lead; b)rings connected to a common external inlaid lead; and c) separate ringsets connected respectively to a first and a second external inlaidlead. In FIGS. 12( a) and (b), the inlaid electrode is formed ofseparate rings 1202 positioned along a member 1000″ substantially in aplane perpendicular to the member length axis. In these embodiments,each ring is separate and requires a separate isolated feedthrough 1020″in the member wall to connect to the common internally (FIG. 12( a)) orexternally (FIG. 12 (b)) threaded stimulation mechanism lead 1042,threaded through an internal isolated channel 1044 in the implantmember. In FIG. 12( c), there are two sets of inlaid electrodes 1202′and 1202″, staggered so that each ring 1202′ lies between two 1202″rings and vice-versa. Each set of rings is connected to a common lead(1042′ and 1042″ respectively), each lead connected through afeedthrough (1020′ and 1020″) to the stimulation mechanism in endsection 1008. Electrical shorts between a lead crossing a ring areprevented by an insulator layer as shown in insert A, formed for exampleby local deposition of a thin insulating film on the bottom (in theexample ring 1202′) conductor. The configuration in FIG. 12( c) removesthe need to have the member itself as an electrode, for example in thecase when it is non-conductive or not conductive enough. One example ofa non-conductive member is shown in cross-section in insert B: atitanium member may for example have a thick enough porous titaniumoxide layer on the surface, formed to enhance mechanical bonding of themember to the bone tissue. In this case, an inlaid electrode may beinlaid in the oxide layer. The electrode external surface may besubstantially flush with the external surface of the oxide, thuspresenting a very minor disturbance to the normal appearance, feel andfunction of the implant member. In other words, the exterior texture ofthe implant is essentially unchanged from that of a regular (notelectrically functionalized) implant. A similar “double inlaidelectrode” configuration may be provided using two of the spiralwindings of FIG. 10, running parallel to each other such that they donot ever cross each other (not shown). More generally, the double inlaidelectrode geometry may be applied to any embodiment described herein, inthe case the implant member itself is either non-conductive or notconductive enough to serve as an electrode.

FIG. 13 shows yet another embodiment in which an inlaid electrode isformed of separate dots 1302 distributed arbitrarily on the implant in amanner operative to provide an optimal current distribution in thetissue. As in the embodiment of FIG. 12, a separate isolated feedthrough1304 in the member wall is needed to connect each dot to the commonstimulation mechanism lead. The common lead may extend from the powersource of the stimulation mechanism through an internal small-boreinsulated hole 1044 that runs the length of the member, meeting atappropriate points lateral holes leading to the feedthroughs (notshown). The formation of internal bores inside a solid member, and theformation of thin insulating layers inside small bores (for example bychemical vapor deposition) are well known in the art.

It will be apparent to one skilled in the art that the shape,dimensions, pitch (or the distance between parallel lines in FIG. 11 orrings in FIG. 12 and electrical properties of the thin wire or ribbonelectrode can be chosen such that they provide the required stimulationin response to an electrical input (voltage or current). For example,the wire diameter or the largest dimension in its cross section may varyfrom a few microns to a few mm. The pitch may also vary (depending onthe wire diameter) from being slightly larger (e.g. by a few microns)than the wire diameter to about 1000 times the wire diameter. It willalso be apparent that the electric field and current distribution in thetissue in contact with the implant may be mapped using calculations orsimulations. Accordingly, the optimum configuration of the inlaidelectrode may be determined for every required stimulation condition.Advantageously, the inlaid electrode of the present invention causesminimal changes in the mechanical strength of the implant, since only aminimal amount of material is removed to form the groove in which theinlaid electrode is positioned. The thickness of the insulator may varyfrom being as thin as a few tens of Angstroms to any thickness.Accordingly, the groove must be larger (in either width, depth, or both)by at least a few tens of Angstroms and up to a few tens of microns thanthe wire diameter or width. It is apparent, as mentioned with referenceto FIG. 4( c), that the inlaid electrode, in its various embodiments,may be used equally well in dental implant members.

A major advantage in having an end section 1008 housing the stimulationmechanism is that in the normal use of an orthopedic implant, thissection is not functionally important. That is, the end section of e.g.a hip implant does not normally have to bind to the bone. In theembodiments of FIGS. 10-13, section 1008 is hollow, with an internalspace configured to contain stimulation mechanism 1030 comprised of apower source (either a battery or energy storage means for coupling toexternal power generators, see e.g. U.S. Pat. Nos. 4,549,547 and4,467,808 to Brighton) and a stimulation electronic device. In general,the stimulation mechanism described in detail with reference to dentalimplants may serve as well in non-dental implants. Section 1008 has anon-conducting envelope 1032 and is connected to member 1002 through aconductive mechanical element 1034, e.g. a screw screwed into member1002. In this case, electrical lead 1040 is connected to the memberthrough element 1034.

Alternatively, end section 1008 may in essence be similar to the dentalabutment described in detail above in its various embodiments, being nowconnected to a non-dental implant (member 1002) instead of a dentalimplant member. In this case, the electrical connections to the memberbody and to the inlaid electrode(s) can similarly be done through,respectively, screw 1034 and feedthrough 1020. If envelope 1032 is notelectrically isolated from member 1002, the inlaid electrode may beformed also on the end section, after the feedthrough surface isproperly treated to form an insulator 1044 that isolates the envelopefrom the inlaid electrode. Preferably, the shape and size of the endsection is designed so that it minimally affects the surgical procedure.

It is appreciated that although the placing of the stimulation mechanismin an end section of an implant member is an advantageous design choice,the stimulation means may be alternatively placed in a different hollowsection of the implant member. Moreover, it would be appreciated that,in certain embodiments, the stimulation mechanism may be entirelyexternal to the implant, for example implanted separately near theimplant member, or projecting the stimulation signals to the electrodesfrom outside the body.

Returning now to FIGS. 12 and 13, rings 1202 and dots 1302 arepreferably made of gold, platinum, or any other suitable highlyconductive biocompatible substance. As in the embodiments of FIGS. 10and 11, the rings are preferably flush with the external surface of themember and have the same texture and feel, thus causing minimumdisturbance in the surface texture as compared with a regular implant.

As orthopedic (e.g. hip) implants are normally much larger than dentalimplants and abutments, the stimulation mechanism for orthopedicimplants may be in general similar to those in typical modern heartpacemakers, in both size and function. That is, an internal power sourcemay preferably be a lithium battery of the type used in pacemakers, andthe electronic device that provides the required electrical signals tothe electrodes includes control means. These means may include anintegrated circuit microprocessor operative to receive external (to thebody) instructions, for example by RF signals, and circuits designed toprovide a variety of signal waveforms to perform electrical stimulation.Stimulation mechanisms described in prior art, e.g. in U.S. Pat. No.6,605,089B1 to Michelson, may also be used in the orthopedic implants ofthe present invention.

FIG. 14 shows another embodiment of a functionalized implant in which(as in FIG. 12( c)) the implant member is not conductive enough to serveas an electrode. This embodiment uses two inlaid electrodes 1402′ and1402″ that crisscross each other. In the overlapping sections, thestructure is similar to the “dual damascene” structure described withreference to insert A in FIG. 12( c).

FIG. 15 shows the device of FIG. 10 in an embodiment in which thefunctionalized implant uses direct currents to induce osteogenesis. Inthis case, the body (member 1002) is held at a negative bias relative tothe inlaid electrode. Once implanted in the body, the stimulationmechanism is activated to provide DC currents in a plurality ofelectrical paths 1502 established externally to the implant between theinlaid electrode and the member. In other embodiments in which thefunctionalized implant uses AC and pulsed currents to induceosteogenesis, the stimulation mechanism includes similar circuits tothose described above, and their preferred parameter ranges are similarto those disclosed above for the dental implant. As with heart pacers,the various electrical parameters (“on”, “off”, length of variousstimulation cycles, etc) are externally controllable.

All publications, patents and patent applications mentioned in thisspecification are herein incorporated in their entirety by referenceinto the specification, to the same extent as if each individualpublication, patent or patent application was specifically andindividually indicated to be incorporated herein by reference. Inaddition, citation or identification of any reference in thisapplication shall not be construed as an admission that such referenceis available as prior art to the present invention.

While the invention has been described with respect to a limited numberof embodiments, it will be appreciated that many variations,modifications and other applications of the invention may be made. Forexample, although the description focuses on dental and hip implants,other implants, specifically other orthopedic implants and in particularknee implants may equally well be implemented with devices as describedabove.

1-92. (canceled)
 93. A device comprising: an implant arranged forimplantation within a bone structure, said implant comprising a firstsection and a second section, wherein said second section comprises ahollow inner space and wherein said first section and said secondsection cooperate such that the hollow inner space is sealed, saidimplant exhibiting a substantially smooth solid outer surface; a firstgroove extending through said outer surface of said implant; anelectrical stimulation mechanism constituted of a power source and anelectronic device in communication with the power source, saidelectrical stimulation mechanism exhibiting a first and a secondelectrical contact of opposing polarity, said electrical stimulationmechanism ensconced within said sealed hollow inner space; a firstconductor inlaid in said first groove and electrically connected to saidfirst electrical contact, said inlaid first conductor substantiallyexternally flush with said outer surface of said implant; and a secondconductor connected to said second electrical contact and in electricalcontact with a portion of the bone structure, said second conductor notsubstantially extending past said outer surface of said implant, whereinsaid electronic device is arranged to provide controlled stimulationsignals to the bone structure via said first and second electricalconductors.
 94. The device according to claim 93, wherein said implantis elongated and said second section forms an end of said elongatedimplant.
 95. The device according to claim 94, wherein said secondsection exhibits a non-conducting envelope and a feedthrough, thenon-conducting envelope forming the outer surface of said secondsection, said first conductor passing through the feedthrough of thenon-conducting envelope.
 96. The device according to claim 93, whereinsaid outer surface of at least one of said first section and said secondsection is electrically conductive, said second conductor constituted ofsaid electrically conductive outer surface, and wherein the inner wallsof said first groove are coated with an electrical insulated separator,such that said inlaid first conductor is electrically insulated fromsaid second conductor.
 97. The device according to claim 96, whereinsaid electrically conductive outer surface comprises titanium.
 98. Thedevice according to claim 96, wherein said electrical insulatingseparator comprises one of: a deposited thin film; an anodically grownthin film; and an inlaid biocompatible non-conductor.
 99. The deviceaccording to claim 93, further comprising a second groove extendingthrough said outer surface of said implant, said second conductor inlaidin said second groove and electrically insulated from said firstconductor inlaid in said first groove.
 100. The device according toclaim 93, wherein said first groove is substantially ring shaped and atleast partially encircles said substrate.
 101. The device according toclaim 93, wherein said first groove is substantially a straight lineextending at least partially along the length of said substrate. 102.The device according to claim 93, wherein said first groove issubstantially tubular and extends longitudinally from inside saidsubstrate through said outer surface.
 103. The device according to claim93, wherein said first groove is spiral shaped.
 104. The deviceaccording to claim 93, wherein said first groove comprises a pluralityof first grooves substantially uniformly distributed about saidsubstrate.
 105. The device according to claim 93, wherein saidstimulation signals include voltage signals selected from the groupconsisting of alternating current voltages, direct current voltages andpulsed voltages.
 106. The device according to claim 105, wherein saidvoltage signals are in the range of 100 μV to 1V.
 107. The deviceaccording to claim 105, wherein said voltage signals produce alternatingcurrents with a frequency in the range of 1 Hz to 100 KHz.
 108. Thedevice according to claim 105, wherein said voltage signals producealternating currents with a frequency in the range of 10 Hz to 20 Hz.109. The device according to claim 93, wherein said electronic device isin communication with a control means and responsive to the controlmeans to adjust parameters of the provided stimulation signalsresponsive to said control means.
 110. The device according to claim109, wherein said parameters comprise pulse amplitude and pulseduration.
 111. The device according to claim 110, wherein saidelectronic device is further responsive to the control means toalternately active the stimulation signals, and cease the stimulationsignals.
 112. The device according to claim 93, wherein the power sourcecomprises an energy storage means.